When drilling through subterranean and geological formations, specialized drilling fluids, referred to as “muds,” are used to help maintain well control and to remove drill cuttings from the hole. The drilling pipe or string can become stuck in the hole, causing catastrophic delays in drilling, significant loss of time and money. There are a number of causes which may contribute to the stuck drill pipe problem including hole cave-in, blow-outs, mud or filter cake buildup in the bore hole. It is essential to free the stuck drill pipe as quickly as possible, with the least amount of down time and the least amount of damage to equipment, the environment and the operators.
Historically, either water-based muds (WBMs) or oil-based muds (OBMs) have been used for offshore wells. Recently, in response to U.S. Environmental Protection Agency (EPA) regulations and drilling-waste discharge requirements imposed by North Sea nations, the drilling industry has developed several types of synthetic-based muds (SBMs) that combine the desirable operating qualities of OBMs with the lower toxicity and environmental impact qualities of WBMs.
Each drilling fluid has positive and negative features. For example, on the positive side, water-based muds (WBMs) do not release free oil, are usually without toxic contaminants such as cadmium and mercury, are typically discharged at the well site and are widely used in shallow wells and in shallower portions of deeper wells; however, on the negative side, in deep or extended-reach wells, the performance of WBMs is often poor. Thus, for deep well intervals and complex drilling situations, oil-based muds (OBMs) and synthetic-based muds (SBMs) are needed for their superior performance.
The problem with OBMs is that U.S. Environmental Protection Agency (EPA) guidelines prohibit release of free oil, as detected by the static sheen test, from drilling fluids and drill cuttings discharges. Thus, OBMs must be recycled and cannot be discharged on-site, so there is the added cost of hauling and disposing of wastes onshore and long-term liability concerns associated with onshore disposal sites. OBMs also pose greater risk to workers through skin irritation and the effects of inhalation. Thus, despite their unique and valuable properties widespread use of OBMs is severely limited.
With regard to synthetic-based muds (SMBs), the synthetic liquid forms the continuous phase, while brine serves as the dispersed phase. The synthetic based fluids are classified according to the molecular structure as, esters (synthesized from fatty acids and alcohols), ethers, usually synthesized from alcohols (U.S. Pat. No. 4,614,235 to Keener et al.), polyalphaolefins (manufactured by the catalytic polymerization of linear alpha-olefins), olefin isomers (manufactured by selective isomerization of normal alpha-olefins) and other base compounds are reported.
An oil-based stuck pipe additive containing propoxylated C18-C32 alkanols, an oil-soluble emulsifier-wetting agent and if desired an imidazoline for high temperature emulsion stability is reported in U.S. Pat. No. 4,436,638 and U.S. Pat. No. 4,464,269 to Walker et al.
SBMs have a wide range of chemical properties, drilling performance and environmental impacts, advantages and disadvantages for drilling operations and disposal of cuttings. For example, SBMs have drilling and operational properties similar to OBM systems and are used where OBMs are commonly used in difficult drilling situations, such as, high downhole temperatures, hydratable shales or salt, where the properties of WMBs would limit performance. Experience has shown that SBMs have higher cost, superior drilling performance and lower environmental to impact than OBMs. SBMs must be recycled, with only the cuttings and a small amount of associated drilling fluids being disposed of on-site, if EPA and other environmental regulations will permit. Since 1990, several low-toxicity, biodegradable SBMs have entered the market. However, restrictions on discharge of cuttings may pose a barrier to their use.
U.S. Pat. No. 5,247,992 to Lockhart describes a fluid for releasing stuck drill pipe that contains one or more carboxylic acids with specific chemical and physical properties.
In U.S. Pat. No. 7,033,976 B2 to Guzman a fluid system additive for use in hydrocarbon exploitation used a biopolymer derived from at least one species of the banana family that allegedly reduces the costs and environmental effects of existing additives.
Nonetheless, a drilling mud or stuck pipe additive is still needed by the drilling industry that provides superior drilling performance, low environmental impact, no release of oil, reasonable cost, and no toxicity to man or the environment.
The present invention fulfills many of the needed attributes of a stuck pipe additive and provides a fluid system additive that supports and improves the efficiency of a water-based mud (WBM) system for the drilling industry.